For me some points to be solved before a more formal review:
* typo on "Release: 10%{?dist}" for a first try :)
* is it standard to use desktop-file-validate on %check ? (I use it on %build)
koji build : http://koji.fedoraproject.org/koji/taskinfo?taskID=3358761
Problems:
+ desktop-file-validate /builddir/build/BUILDROOT/step-4.7.0-10.fc16.i386/usr/share/applications/kde4/step.desktop
/builddir/build/BUILDROOT/step-4.7.0-10.fc16.i386/usr/share/applications/kde4/step.desktop: error: (will be fatal in the future): value "Physics" in key "Categories" in group "Desktop Entry" requires another category to be present among the following categories: Education;Science
warning: File listed twice: /usr/share/doc/HTML/en/step

I personally prefer using desktop-file-* in either %install or %check.
Anyway, as that is still (currently) non-fatal, let's not block the review on it (though I will poke upstream to get it fixed properly).